1. Field of the Invention
The present invention relates to an indicating instrument for driving an indicating needle by a stepping motor.
2. Related Art Statement
Conventionally, by way of an example, a stepping motor has been used as a source of power for turning an indicating needle of an instrument board and so on of an automobile and the like. The stepping motor is configured such that the rotation of the stepping motor is transferred to the indicating needle by using a reduction gear, and then the indicating needle indicates vehicle speed, engine revolution, and so on.
However, such a stepping motor may produces missed steps by various reasons. As a device for carrying out a missed step reset, a stopper projection is provided in the indication board on which the stepping motor is mounted. The stopper projection is provided in a position where the indicating needle of the indicating board starts the turning. When the stepping motor produces the missed steps, the indicating needle is returned to the stopper projection side by outputting a zero reset signal to the stepping motor, and when the indicating needle comes into contact with the stopper projection, it is determined that the missed step reset is completed, then the zero reset signal is stopped (reference to Japanese Patent Laid Open Nos. 2001-314099, 2002-250641).
However, regarding conventional stepping motor control for an indicating instrument, when the indicating needle comes into contact with the stopper projection, the processing of missed step reset is completed by stopping the output of the zero reset signal with a state that the indicating needle is pressed onto the stopper projection. Therefore, when the reduction gear includes the allowance in a stopped position, there may be a case that an appropriate position which should be originally stopped is deviated by the allowance of the gear with the backlash of the reduction gear; even after the missed step is eliminated, there was a case that the indicating needle did not indicate an appropriate position.